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Japanese knotweed – Davies v Bridgend CBC – a welcome decision for defendants

The judgment provided much needed clarity on recoverability of damages for diminution in value in Japanese knotweed cases.

The Supreme Court has unanimously overturned the Court of Appeal decision in Davies v Bridgend County Borough Council [2023] UKSC 16 that a defendant was responsible for residual diminution in value of the claimant’s land following the treatment of Japanese knotweed, even where the spread had occurred before the breach. 

The judgment provided much needed clarity on recoverability of damages for diminution in value in Japanese knotweed cases.


The claimant owned a terraced property with a garden that backed onto an embankment. Japanese knotweed was present on the embankment. Evidence showed that it was likely that this had emanated from being dumped over a garden wall by another resident rather than having grown up the embankment. The knotweed had continued to grow and spread, unknown to the defendant council. 

The claimant had purchased the property prior to 2004. Japanese knotweed rhizomes had already spread onto the claimant’s land by the date of purchase. The claimant first became aware of the presence of the Japanese knotweed in 2017 when he received a knock at his door informing him that he may be able to make a claim. No action was taken until a letter of claim was issued in 2019.

First instance decision

Initially, it was held that the date of knowledge of a foreseeable risk of harm was after the 2012 publication of the RICS paper and that from 2013 the council ought to have started treating the knotweed; therefore there was a breach of duty and a continuing nuisance between 2013 and 2018.

Despite a breach having been established, the claimant’s claim for general damages for distress and inconvenience was dismissed. This finding was assisted by the claimant’s lack of action once notified of the presence of Japanese knotweed in 2017. 

The claimant also claimed diminution in the value of the property which included the costs of treatment, disturbance and inconvenience, neighbour cooperation and temporary loss of land. The heads of loss were either conceded, not pursued or found to be irrecoverable. This left a claim for residual diminution in value after the treatment concluded. 

At first instance it was found that the claim for residual diminution in value was irrecoverable because it was pure economic loss, and the tort of nuisance did not exist to protect economic interests. The claimant appealed. 


The Court of Appeal (CA) upheld the initial  decision. The CA found that there would be no nuisance in the absence of actual encroachment and, as such, the presence of Japanese knotweed next door would not be sufficient to ground a claim for pure economic loss. Where there had been actual encroachment, however, then there had been a physical interference with the property, and it followed that a claim for diminution in value was recoverable. 

The claimant had accepted that the cost of treatment would always have been required but for the breach, although argued that residual diminution was, in fact, recoverable as the nuisance was continuing. The council, as expected, did not agree with the claimant’s position. The council contended that there was evidence that the Japanese knotweed rhizomes had encroached onto the claimant’s land prior to 2004, so it made no difference that they had not treated it between 2013 and 2018. The loss therefore preceded the breach. This was rejected by the Court of Appeal. Drawing analogy with the Delaware Mansions case, the CA stated that the mere fact that the encroachment was historic was irrelevant given the ongoing and persistent encroachment. 

The CA decision was problematic. The council considered their position to be simple – if the breach had not caused the loss, then how was it that damages were recoverable? 

The matter came before the Supreme Court. The Supreme Court unanimously overturned the Court of Appeal decision. Lord Stephens, in the leading judgment, stated:

“If the diminution in value would have occurred in any event, then the defendant’s breach of duty is eliminated as a cause of the diminution in value so that there would be no casual link between the defendant’s breach of duty and the diminution in value.”

There was no evidence provided to the court that the defendant’s breach of duty between 2013 and 2018 had either increased or materially contributed to the diminution of the claimant’s land. It was accepted that the actual encroachment had occurred many years prior to 2013 and therefore the subsequent breach had no causative consequence.


The Supreme Court judgment is welcomed. It is helpful to defendants in a number of ways.

First, it clearly sets out that the ‘but for’ test for causation applies to causes of action in private nuisance. Any diminution in value that has already occurred prior to any breach is not recoverable. The council’s stance on this aspect was simple and ought not to have been overcomplicated. The decision brings much needed simplicity to such cases. 

Second, it reaffirms the position as regards limitation in that Japanese knotweed is not a continuing nuisance and encroachment more than six years before the claim was brought rendered it statute-barred, whether or not the nuisance was continuing. 

Finally, it provides a helpful summary/clarification of the Delaware Mansions case in that a claim for diminution was not a reasonable cost incurred to abate the nuisance and that it was not authority for losses to be recoverable if they occurred prior to the defendant’s breach of duty.

It will be interesting to see how claimant firms react to the decision. Clearly, the case should impact on the extent of claims being pursued and potentially limit a significant number of claims being brought to allocation to the small claims track. That being said, unanswered questions remain in respect of Japanese knotweed claims:

  1. Whether encroachment of Japanese knotweed is a continuing nuisance.
  2. Whether the reputation of Japanese knotweed is undeserved and ought to be reclassified.
  3. The implications of Japanese knotweed having encroached onto land prior to purchase.

It is therefore unlikely such claims will go away. However, the extent of such claims should be limited.

For more information/insights concerning Environmental Claims please contact Andrew Clarke, Partner, who heads the Environmental Claims Technical Unit or Rachael Fawcett.

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